Method and apparatus for heavy-media separation



y 0, 1956 H. HARDINGE 2,753,998

METHOD AND APPARATUS FOR HEAVY-MEDIA SEPARATION Filed May 3, 1950 2 Sheets-Sheet 1 FIG. I.

I9 I? I8 SINK FLOAT l 9 1 l2 DRAINAGE SCREEN J DRAINAGE SCREEN I I I MEDIA SINK FLOAT MEDIA .I

I0 1 WASH sGREEN WASH sGREEN I I DRAINAGE DRAINAGE I' SINK FLOAT CLEANING GIRcuIT DENSIFIER THICKENED MEDIA INVENTOR. HARLQWE HARDINGE Aria/W096 y 1956 H. HARDINGE 2,753,998

METHOD AND APPARATUS FOR HEAVY-MEDIA SEPARATION Filed May 5, 1950 2 Sheets-Sheet 2 INVENTOR. HARLOWE HARDINGE United States Patent METHOD AND APPARATUS FOR HEAVY-MEDIA SEPARATION Harlowe Hardinge, York, Pa., assignor to Hardinge Company, Incorporated, York, Pa., a corporation of New York Application May 3, 1950, Serial No. 159,829

7 Claims. (Cl. 209-1725) This invention relates to a method and means for heavymedia separations of ore concentrations, and more especially to a method and means of the type described in which a counter-current separator is employed. The Hardinge counter-current classifier can be adapted for use in this process.

As a result of relatively recent developments, heavymedia separations have proved particularly effective in the treatment of low grade ores, coal, and certain other types of materials which cannot be processed economically by older mineral dressing methods. For example, iron and manganiferous iron ores have been successfully treated by these methods, as have various lead and zinc ores. The use of a process including a counter-current separator has proved especially effective for this purpose.

In general, the invention relates to a heavy density media separation process in which the sink material is moved mechanically to discharge out of a pool of the media and the float material is moved to discharge out of the pool by a flow of media counter-current to the direction of movement of the sink material. The media discharged at both the sink and float ends of the countercurrent separator is then cleaned and thickened and a portion of the thickened media together with added water is returned to the float end of the classifier. Another portion of the thickened media together with added water is returned to the sink discharge end of the separator.

An important feature of the invention resides in the regulation of the specific gravity of the media in either end of the pool, as well as the entire pool. This is possible because the pool is separated into compartments in a manner which will be subsequently described.

In order to make the invention more clearly understood, an embodiment is shown in the accompanying drawings. It is understood, however, that the embodiment shown in the drawings is by way of illustration only and various changes can be made therein, by those skilled in the art, without departing from the spirit of the invention.

In the drawings:

Figure 1 is a diagrammatic flow sheet of an arrangement of equipment utilized in performing a heavy-media separation according to the present invention;

Figure 2 is a vertical section of a Hardinge countercurrent classifier; and

Figure 3 is a fragmentary sectional view of the sink end of the classifier shown in Figure 2.

The practice of the present invention is best understood by citing a typical treatment. In this example, an iron ore from the Mesabi range, and comprising a mixture of iron ore and gangue minerals, was selected as the product for treatment. The heavy-media employed in the operation was ferro-silicon having a specific gravity of about 6.7, but employed in varying degrees of density throughout a continuous operation. However, other densifying media, such as sand and the like, could be employed.

In the procedure shown in Figure 1, separate supplies of media, ore and water indicated by the numerals 1, 2

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and 3, respectively, are fed into the slightly inclined counter-current separator 4 at a point 5 between the ends of the classifier 4 and above the pulp level. Additional supplies of water and media identified by the numerals 6 and 7, respectively, are fed into the sink discharge end of the separator. This mixture forms a counter-current to the direction of movement of the sink concentrate.

The sink concentrate is discharged from the classifier at 8 and passes to a drainage screen 9 where it is separated from the media. The sink concentrate then passes to a wash screen 10. After being washed, the sink concentrate is discharged at 11 as the final product of the treatment.

The float product of the heavy-media separation passes to a drainage screen 12 where the heavy density media is separated from the float. The remaining light density liquid is passed through a wash screen 13 where the float material 14 is separated and discarded and the light density media is conveyed to a cleaning circuit 15. There it is joined by the light density media from the wash screen 10.

The cleaning circuit 15 may include a magnetic separator or other means of separation to remove the tailings from the light density liquid. These tailings are discarded and the light density liquid media is then conveyed to a densifier 16. The thickened media from the densifier 16 and the heavy media from the screen 12 are then collected at 17. The media from the screen 9 is also collected at 17. This collected material is fed through regulating valves 18 and 19 to the feed inlets 1 and 7, respectively, of the feed separator 4. The water fed to the separator 4 is controlled by valves 20 and 21.

The counter-current separator 4 forms an important feature of the invention. The type of counter-current separator shown in Figures 2 and 3 is a Hardinge counter-current classifier which has been adapted for use in heavy-media separation.

This separator, which is generally designated by the numeral 4, comprises a rotatable tank 25 provided with spaced annular tires 26 which are driven by friction rollers 27. The friction rollers 27 are fixed to a shaft 28 which is rotated through a sprocket and chain 29 by any suitable source of power. The shaft 28 is mounted between bearings 30. Of course, the tank 25 can be rotated by any other suitable mechanism such as a ring gear, if desired.

The inner surface of the tank 25 is provided with a spiral 31. An important feature of the separator is the fa zlt1 that the spiral 31 is attached to the tank and revolves wi it.

The previously described ore from source 2 is fed into the float end of the separator 4 through a launder 32 and is discharged from the launder at a point above the pulp level. The heavy media from source 1 and the water from source 3 are discharged from nozzles 33 and 34, respectively, into the feed launder 32 and enters the pool with the ore.

During the continued rotation of the tank 25, the coarse particles settle out and are moved forward by the spiral 31 and are repeatedly turned over during this forward movement. As a result, the light siliceous matter rises to the surface while the heavy iron ore and some heavy ferro-silicon material continue their forward motion. The fines, wash water and media forming the float are then washed backward towards the float end of the classifier by the mixture of media from source 7 and water from source 6 entering the sink discharge end of the separator 4 through the nozzles 35 and 36, respectively. This counter-current causes the float to overflow from the wait or lip 37 provided in the float end of the separator 4. It then is conveyed to the drainage screen 12 for separation, in the manner which has been previously described.

In order to obtain maximum separation it is necessary to regulate the specific gravity of the pool. This can be ac ompl sh d n a numb r 9f ways T e ssls t d means will depend upon the material being treated and the results that are desired.

The angle of the separator 4, the speed of its rotation, and the rate of feed of the ore to the separator can all be varied. This will have a definite effect on the specific gravity of the pool. For example, it has been found that crowding the separator in any of these ways will increase the middling being depressed sufficiently for it to be taken into the sink.

An increase in the volume of counterflow will also force the float towards the float end. Such an increase will therefore improve separation under some conditions.

The control of the media entering the pool is especially important. This can be controlled at either or both ends of the tank. Control at one end is effective because the tank is divided into compartments by the spiral flights 31. The submerged part of the flights divide the pool in the same manner.

The spiral flights are of variable pitch and depth. The pitch decreases and the depth of the flights increases towards the sink discharge end. For this reason, the volume between succeeding troughs formed by the spiral decrease as the sink discharge end is approached.

As a result, the settled solids are moved into sections of decreasing volume and the liquid is forced to flow over the top of the last flights, leaving the concentrate with some entrained moisture and media to be removed from the separator through the discharge launder 38.

This structure enables a close control of the difference in specific gravity of the media in the sink and the float end by regulation of the media fed into one or both ends of the separator. This can be advantageous. For example the specific gravity of the media in the sink end of the pool can be lowered (as compared to the specific gravity of the media in the remainder of the pool) to cause the suspended middlings moved to that region to sink and be discharged with the sink concentrate, if it is desired to recover these middlings. The same effect can be obtained if the specific gravity at the pool end is raised so that it is higher than the specific gravity of the media at the sink end of the pool. In both instances it is assumed that the specific gravity of the middling is not less than the apparent specific gravity of the material to be rejected. Moreover, a high specific gravity of media at the float end will cause the float to report to the float end.

As the flights form compartments, the pulp cannot flow directly from one to the other, especially when the separator is fully raised. Thus change in specific gravity at one or both ends of the tank will result in a difference in specific gravity in the several parts of the tank.

The advantages of the described method and apparatus are numerous. The rolling action of the drum maintains a more uniform density of the media throughout the main body of the pool than can be obtained by the use of the spiral, drag or rake type of separator. This rolling action of the sink product also frees trapped float to greater degree than do the previously mentioned types of separators. In addition, the counterflow of media from the discharge end over the exposed last turn of the spiral 31 prevents float from reaching the sink discharge launder 38 when the tank is inclined. This also permits the media in the sink discharge head to be maintained at a difierent specific gravity from the pool. This is different from the dry deck of the spiral, drag or rake type of separator or of the drum type separator having parallel lifters. In these separators the middling is forced or crowded to the area where the pool meets a dry deck. At this point, the specific gravity of the media is highest and much of the middling is forced out due to its lighter gravity and is discharged as a separate product.

Furthermore, it should be noted that the overflow weir or lip 37 of the disclosed apparatus is small with respect to the flow. For this reason, it has considerable depth as compared with the larger areas of overflow that usually occur with other types of separators. Also this lip rotates with the drum' 25. As a result, the coarse light material of the size greater than the depth of the overflow liquid coming against the lip Will tend to be pushed by the rotating lip into the float discharge and the pool depth at the center point of discharge will be deeper than is the case where the lip has an increased area which decreases the depth.

It is believed obvious that the described method and apparatus is ideal for heavy-media separation because a controlled specific gravity is maintained throughout the pool to form a sink, float and a true middling, and these are separated by the rotation of the drum, the use of an exposed flight to prevent the float from reaching the sink discharge end, and the control of the relative specific gravities of the media in the different zones of the pool.

While a selected form of the invention has been shown, it is to be understood that the method and apparatus is susceptible of variations in construction and operation without exceeding the scope of the appended claims. I

I claim;

1. In a heavy density media separation process, the steps of feeding ore, media and water to the main body of a pool, moving the sink material mechanically through the pool to discharge out of the pool, moving the float material to discharge out of the pool by a flow of media counter-current to the direction of movement of the sink material, cleaning the media discharged with the materials, thickening the cleaned media, returning a portion of the thickened media together with water to the main body of the pool, returning another portion of the thickened media together with water to the pool adjacent the point of sink discharge, and controlling the proportion of incoming media and water to maintain a difference in the specific gravity of the media in the portion of the pool adjacent the point of sink discharge as contrasted to the specific gravity of the media of the main body of the pool.

2. In a heavy density media separation apparatus, an inclined and rotatable tank having an annular compartment of increased diameter at its higher end and said tank containing a pool of media, a feed launder having a discharge intermediate the higher and lower ends of the tank, an overflow weir at the lower end of the tank for discharging float material, a spiral attached to the interior of the tank for moving sink material to discharge from the higher end of the tank, means for introducing media andwater to the feed launder, separate means for introducing media and Water to said annular compartment adjacent the discharge for the sink material and means for regulating the media and water feed into both ends of the tank to maintain a difference in the specific gravity of the media within the pool adjacent the point of sink discharge as contrasted to the specific gravity of the media of the main body of the pool.

3. In a heavy density separation apparatus, an inclined and rotatable tank containing a pool of media, a feed launder having a discharge intermediate the higher and lower ends of the tank, an overflow weir at the lower end of the tank for discharging float material, a spiral attached to the interior of the tank for moving sink material to discharge from the higher end of the tank, separate means for introducing media and water to the feed launder, separate means for introducing media and water to the pool adjacent the discharge for the sink material, means for cleaning media discharged with the sink and float material, means for thickening at least a portion of the cleaned media, and means for returning the thickened media to the pool through the feed launder and also adjacent the discharge for the sink material.

4. in a heavy density media separation process, the steps of feedingore and media and water to a pool, moving the sink material separating from the ore mechanically through the pool to discharge out of the pool into a compartment separated from the pool, moving the float material to discharge out of the pool by a flow of media countercurrent to the directirn of movement of the sink material, feeding media and water to the compartment, decanting media and Water from the compartment into the pool, regulating the rate of addition of media and water into the compartment to control the relative specific gravity of the media and discharging the sink material from the compartment.

5. in a heavy density media separation process, the steps of feeding ore, media and water to a pool, moving the sink material mechanically through the pool to discharge out of the pool into a compartment separated from the pool, moving the float material to discharge out of the pool by a flow of media countercurrent to the direction of movement of the sing material, feeding media and Water to the compartment in proportions to maintain a lower specific gravity of the media in the compartment than in the pool, decanting media and water from the compartment into the pool, and discharging the sink material from the compartment.

6. In a heavy density media separation process, the steps of feeding ore, media and water to a pool, moving the sink material mechanically through the pool to discharge out of the pool into a compartment separated from the pool, moving the float material to discharge out of the pool by a floW of media countercurrent to the direction of movement of the sink material, feeding media and water to the compartment in proportions to maintain a higher specific gravity of the media in the compartment than in the pool, decanting media and water from the compartment into the pool, and discharging the sink material from the compartment.

7. In a heavy density media separation apparatus, an inclined and rotatable tank having an annular compartment of increased diameter at its higher end and said tank containing a pool of media, a feed launder having a discharge intermediate the higher and lower ends of the tank into said pool, means for introducing media, ore and water to the feed launder, a spiral attached to the interior of the tank for moving sink material from the pool to discharge from the higher end of the tank, said spiral dividing the tank into a plurality of compartments of progressively decreasing volume and increasing depth toward the higher end of the tank, means for introducing media and water into said annular compartment of the tank adjacent the sink discharge end, and an overflow weir at the lower end of the tank for discharging float material and media from the tank.

References Cited in the file of this patent UNITED STATES PATENTS 1,392,400 Chance Oct. 4, 1921 1,559,938 Chance Nov. 3, 1925 1,895,504 Wuensch Jan. 31, 1933 2,113,609 Wuensch Apr. 12, 1938 2,136,686 Hardinge Nov. 15, 1938 2,190,637 Rakowsky et al. Feb. 13, 1940 2,347,264 Holt et al. Apr. 25, 1944 2,368,416 Holt Jan. 30, 1945 2,428,777 Bitzer Oct. 14, 1947 2,460,802 Bitzer Feb. 8, 1949 2,474,774 Bean June 28, 1949 

2. IN A HEAVY DENSITY MEDIA SEPARATION APPARATUS, AN INCLINED AND ROTATABLE TANK HAVING AN ANNULAR COMPARTMENT OF INCREASED DIAMETER AT ITS HIGHER END AND SAID TANK CONTAINING A POOL OF MEDIA, A FEED LAUNDER HAVING A DISCHARGE INTERMEDIATE THE HIGHER AND LOWER ENDS OF THE TANK, OVERFLOW WEIR AT THE LOWER END OF THE TANK FOR DISCHARGING FLOAT MATERIAL, A SPIRAL ATTACHED TO THE INTERIOR OF THE TANK FOR MOVING SINK MATERIAL TO DISCHARGE FROM THE HIGHER END OF THE TANK, MEANS FOR INTRODUCING MEDIA AND WATER TO THE FEED LAUNDER, SEPARATE MEANS FOR INTRODUCING MEDIA AND WATER TO SAID ANNULAR COMPARTMENT ADJACENT THE DISCHARGE FOR THE SINK MATERIAL AND MEANS FOR REGULATING THE MEDIA AND WATER FEED INTO BOTH ENDS OF THE TANK TO MAINTAIN A DIFFERENCE IN THE SPECIFIC GRAVITY OF THE MEDIA WITHIN THE POOL ADJACENT THE POINT OF SINK DISCHARGE AS CONTRASTED TO THE SPECIFIC GRAVITY OF THE MEDIA OF THE MAIN BODY OF THE POOL. 